skillscript-runtime v0.18.1

Closes the long-standing asymmetry across the four substrate slots.
Pre-v0.18.1, SkillStore / DataStore / LocalModel each had connectors.json
substrate-section support, but AgentConnector was programmatic-only —
the bootstrap.ts comment explicitly read "agent_connector → null
(adopter wires explicitly)." v0.18.1 brings the slot to parity.

What landed

• New agent_connector?: SubstrateChoice | null field in
  SubstrateConfig (connectors/config.ts)
• New "noop" built-in type — explicit declaration of the no-op
  posture (equivalent to omitting the slot; the Registry's
  getAgentConnectorOrDefault returns NoOpAgentConnector either way,
  but "noop" makes the intent visible in connectors.json)
• "custom" type accepted at parse time, errors at bootstrap with a
  clear message pointing at the programmatic path (mirrors the
  sync-bootstrap limitation on the other three slots)
• New agentConnector?: AgentConnector field in BootstrapOpts +
  DefaultRegistryOpts — programmatic surface for adopters supplying
  an instance (matches the existing skillStore? / dataStore? /
  localModel? symmetry)
• bootstrap() precedence: programmatic opt > declarative substrate >
  default unset (Registry NoOp fallback)
• bootstrap() calls registry.registerAgentConnector("primary", ...)
  with the resolved instance (async; health_check fires at registration
  per existing contract)

Scaffold + adopter guidance

scaffold/connectors.json adds "agent_connector": null with the same
_example_* documentation pattern as the other slots. Examples show
both the noop short-form and the custom object-form (with a comment
linking to examples/connectors/HttpWebhookAgentConnector as a
reference impl).

Tests

11 new tests in v0.18.1-agent-connector-wiring.test.ts covering:
parse of noop / custom / null forms, unknown-type rejection,
short-form-custom rejection, BootstrapOpts wiring, substrate-config
wiring, precedence (opts beats config), custom-via-config error
pointing at programmatic path, fallback to NoOp when neither slot nor
opt supplied.

1682 tests total. Narrow-core LOC ceiling unchanged at 10500.

Adopter-side: substrate-mediated AgentConnector impl

For adopters with a memory-store routing layer or shared agent
inbox/wake substrate: implement the AgentConnector contract
(deliver / wake / list_agents / health_check /
request_response) mapping to the substrate's primitives, then wire
via bootstrap({ agentConnector: new MyAgentConnector(...) }). See
examples/connectors/HttpWebhookAgentConnector for the reference
shape — 320 LOC, end-to-end working, with tests + README.

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